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Binder M.,OSRAM | Nirschl A.,OSRAM | Nirschl A.,University of Regensburg | Zeisel R.,OSRAM | And 6 more authors.
Applied Physics Letters | Year: 2013

We report the direct observation of hot carriers generated by Auger recombination via photoluminescence spectroscopy on tailored (AlGaIn)N multiple quantum well (QW) structures containing alternating green and ultra-violet (UV) emitting (GaIn)N QWs. Optically pumping solely the green QWs using a blue emitting high power laser diode, carrier densities similar to electrical light-emitting diode (LED) operation were achieved, circumventing possible leakage and injection effects. This way, luminescence from the UV QWs could be observed for excitation where the emission from the green QWs showed significant droop, giving direct evidence for Auger generated hot electrons and holes being injected into the UV QWs. An examination of the quantitative relation between the intensity of the UV luminescence and the amount of charge carriers lost due to drooping of the QWs supports the conclusion that Auger processes contribute significantly to the droop phenomenon in (AlGaIn)N based light-emitting diodes. © 2013 AIP Publishing LLC.


Rosener B.,Fraunhofer Institute For Angewandte Festkorperphysik | Kaspar S.,Fraunhofer Institute For Angewandte Festkorperphysik | Rattunde M.,Fraunhofer Institute For Angewandte Festkorperphysik | Topper T.,Fraunhofer Institute For Angewandte Festkorperphysik | And 4 more authors.
Optics Letters | Year: 2011

We demonstrate a 2 μm semiconductor disk laser emitting in a single longitudinal mode with a linewidth in the <10 kHz range. A heterodyne detection scheme was used for precise linewidth measurements. In these experiments, the output beams of two identical laser cavities were superposed in order to generate a beat note signal on a photodiode. In the absence of active frequency stabilization, a linewidth of 45 kHz was measured at an output power of 100mW. When using a frequency stabilization consisting of a feedback loop with a Fabry-Perot interferometer as wavelength reference, the linewidth could be further reduced to 9 kHz. © 2011 Optical Society of America.


Schiavon D.,OSRAM | Schiavon D.,University of Ulm | Binder M.,OSRAM | Binder M.,Fraunhofer Institute For Angewandte Festkorperphysik | And 2 more authors.
Applied Physics Letters | Year: 2013

We report on a green light-emitting device, in which the light of an efficient blue 1 mm2 GaInN/GaN light-emitting diode (LED) is converted into green light by an optically pumped GaInN/GaN multiple quantum well structure. This solution reached an efficacy of 127 lm/W, i.e., higher than that of state-of-the-art 1 mm2 GaInN/GaN LEDs emitting directly at the target wavelength, at 350 mA current and 535 nm peak wavelength. Optically pumped converters overcome the design limitations of typical multiple quantum well LEDs, where carrier transport issues limit the maximum number of functioning wells and might help to solve the problem of the green gap. © 2013 American Institute of Physics.


Rosener B.,Fraunhofer Institute For Angewandte Festkorperphysik | Rattunde M.,Fraunhofer Institute For Angewandte Festkorperphysik | Moser R.,Fraunhofer Institute For Angewandte Festkorperphysik | Kaspar S.,Fraunhofer Institute For Angewandte Festkorperphysik | And 4 more authors.
Optics Letters | Year: 2011

We demonstrate anoptically pumped semiconductor disk laser based on the (AlGaIn)(AsSb) material system, which operates at an emission wavelength of 2:8 μm. Up to 120 mW of output power were obtained in cw operation and more than 500 mW in pulsed mode. The performance of the present laser is discussed in comparison to shorterwavelength semiconductor disk lasers based on the same materials system. © 2011 Optical Society of America.


Smirnov W.,Fraunhofer Institute For Angewandte Festkorperphysik | Hees J.J.,Fraunhofer Institute For Angewandte Festkorperphysik | Brink D.,Fraunhofer Institute For Angewandte Festkorperphysik | Muller-Sebert W.,Fraunhofer Institute For Angewandte Festkorperphysik | And 3 more authors.
Applied Physics Letters | Year: 2010

Nanopores in insulating solid state membranes have recently attracted much interest in the field of probing, characterizing, and manipulating single linear polymers such as DNA/RNA and proteins in their native environment. Here a low cost, fast, and effective way to produce nanostructures such as pyramidal shaped nanopores and nanochannels with dimensions down to about 15 nm in diamond membranes without any need for electron-beam lithography is demonstrated. By use of a catalytic process, anisotropic etching of diamond with self-organized Ni nanoparticles in hydrogen atmosphere at 900 °C is achieved and possible etching mechanisms are discussed. It is shown that diamond planes with the crystallographic orientation of [111] are etched slowest with this method. © 2010 American Institute of Physics.


Smirnov W.,Fraunhofer Institute For Angewandte Festkorperphysik | Kriele A.,Fraunhofer Institute For Angewandte Festkorperphysik | Yang N.,Fraunhofer Institute For Angewandte Festkorperphysik | Nebel C.E.,Fraunhofer Institute For Angewandte Festkorperphysik
Diamond and Related Materials | Year: 2010

Nano-wires have become promising tools in a vast field of applications. Due to the many unique properties of diamond, the use of diamond nano-wires in biosensors attracts increasing attention. In this paper we introduce the realisation of wires from diamond using self-aligned nickel nano-particles as etching mask in an oxygen ICP dry etching step. With this process it is possible to create wires of high aspect ratios of 50, with diameters as small as 20 nm, and typical lengths of up to 1 μm on a large area in a dense pattern of about 10 11 cm - 2. The Ni nano-particles are formed by thermal annealing at 700 °C for 5 min of a thin (1 nm) Ni film that is deposited onto the diamond surface. The surface enhancement factor due to wires is dependent on the geometrical details of wires and was measured to be 10 to 80. The electrochemical properties of wires have been characterized by cyclic voltammetry using Fe(CN) 6 - 3/- 4 which shows that such topographies act as filter for redox molecules. © 2009 Elsevier B.V. All rights reserved.


Zybell S.,Helmholtz Center Dresden | Schneider H.,Helmholtz Center Dresden | Winnerl S.,Helmholtz Center Dresden | Wagner M.,Helmholtz Center Dresden | And 2 more authors.
Applied Physics Letters | Year: 2011

We investigate the time-resolved photoluminescence (PL) dynamics of an undoped GaAs/AlGaAs multiple quantum well under mid-infrared (MIR) irradiation. A time-delayed MIR laser pulse from a free-electron laser, tuned to the intersubband transition energy of the quantum well, induces temporal quenching of the PL intensity with subsequent recovery. The experimental data can be accurately described by a simple rate-equation model, which accounts for the cooling of the non-radiative states to radiative states. By performing polarization sensitive measurements, we are able to discriminate the contributions of free-carrier absorption from that of intersubband absorption, where the latter is about 50 times more efficient. © 2011 American Institute of Physics.


Minkevicius L.,Lithuanian Academy of Sciences | Tamosiunas V.,Lithuanian Academy of Sciences | Kasalynas I.,Lithuanian Academy of Sciences | Seliuta D.,Lithuanian Academy of Sciences | And 5 more authors.
Applied Physics Letters | Year: 2011

Room-temperature detection and imaging in transmission and reflection geometries at 0.591 THz with planar asymmetrically shaped InGaAs diodes (also called bow-tie diodes) are demonstrated in direct and heterodyne mode. The sensitivity of the diodes is found to be 6 V/W in direct mode, and the noise-equivalent power (NEP) in direct and heterodyne mode is estimated to be about 4 nW/√Hz and 230 fW/Hz for a local-oscillator power of 11 μW, respectively. The improvement of the dynamic range by heterodyning over direct power detection amounts to about 20 dB using pixel read-out times relevant to real-time imaging conditions. © 2011 American Institute of Physics.


Worl A.,Fraunhofer Institute For Angewandte Festkorperphysik | Rehm R.,Fraunhofer Institute For Angewandte Festkorperphysik | Walther M.,Fraunhofer Institute For Angewandte Festkorperphysik
Infrared Physics and Technology | Year: 2013

We characterize the low-frequency white noise behavior of a large set of InAs/GaSb superlattice infrared pin-photodiodes for the mid-wavelength infrared regime at 3-5 μm. For diodes with an increased dark current in comparison to the dark current of generation-recombination limited bulk material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre's noise model for avalanche multiplication processes is compliant with our data. We suggest that within high electric field domains localized around macroscopic defects, avalanche multiplication processes leading to increased dark current and excess noise. © 2013 Elsevier B.V. All rights reserved.


Kaspar S.,Fraunhofer Institute For Angewandte Festkorperphysik | Rattunde M.,Fraunhofer Institute For Angewandte Festkorperphysik | Tpper T.,Fraunhofer Institute For Angewandte Festkorperphysik | Manz C.,Fraunhofer Institute For Angewandte Festkorperphysik | And 2 more authors.
Applied Physics Letters | Year: 2012

We report on an optically pumped single-mode GaSb-based semiconductor disk laser (SDL) emitting at 2.05 μm at an output power of 960 mW (1100 mW) with a side-mode suppression of better than 30 dB (20 dB). A linewidth of 60 kHz (sampling time: 100 μs) was measured at an output power of 960 mW. This improvement in output power over previous reports, which was achieved via a careful design of the SDL cavity paying close attention to the spatial overlap between cavity mode and pump spot, makes this class of SDL particularly attractive for remote sensing and optical free-space communication. © 2012 American Institute of Physics.

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